Move action filter logic to LogPager

Move action filter logic to LogPager

This moves the action filtering logic from SpecialLog to LogPager,
in a limitAction function, as this seems to be how this is done
for other params (title, performer, etc).
This also uses $pager->getPerformer and getTagFilter() for resp.
performer and tag filter as the options to show, rather than the
raw request values (in a WYSIWYG logic).

Change-Id: I4918a8a2dca3fdbadd7d65c9c9972e6f67a1761b